RHIZOGENESIS PRETREATMENTS AND EFFECTS ON MICROCUTTINGS DURING TRANSITION

Pre-root and rooting treatments can each exert a strong influence on subsequent transplant adaptation of microcuttings. In vitro rhizogenesis favored shoot development for herbaceous and woody microcuttings, but resulted in underdeveloped roots for woody species, and no secondary vascular cambium activity until after ex vitro transplant. Herbaceous plants, which typically don't develop secondary vascular growth, produced normal roots in vitro. The results suggest that in vitro rooting may not be a post-transplant handicap for herbaceous plants. A double phase (liquid overlay) system for three cultivars of Rosa chinensis minima was tested as a means to capitalize on both in vitro benefits to shoot quality and the tendency for superior root structure ex vitro. Liquid overlay significantly enhanced the shoot length, area, and fresh weight of microcuttings, and improved subsequent ex vitro rooting efficiency up to 18%. The overlay treatment suggests a method to achieve longer cuttings and extend the in vitro shelf life of shoot cultures to coincide with production scheduling guidelines.